Therapeutic monoclonal antibodies (McAbs) exhibit tremendous potential to treat human disease such as cancer and rheumatoid arthritis. More than 300 antibodies are undergoing clinical development and 2915 clinical studies involving antibodies are being carried out. The effect of therapeutic antibodies is concentration dependent. However, in some patients, therapeutic antibodies can be rapidly eliminated from the body and will be of little benefit to the patient. If a patient could have benefited from, but was not given an alternative therapeutic, then the patient's disease could have worsened or become life threatening during the course of therapeutic antibody treatment. However, if a physician can use the results of an assay to readily determine therapeutic antibody concentration, then the physician can adjust treatment to the benefit of the patient. Traditional immunoassays (e.g. enzyme-linked immunosorbant assays or ELISAs) typically incorporate antigens to detect antigen-specific antibodies in serum samples. However, the antigens recognized by many therapeutic antibodies can be unstable, difficult to work with or expensive to acquire. As such, they cannot always be used to build a simple, stable, reproducible assay. Therapeutic antibodies have been engineered or developed to assume most, if not all of the immunological features of a normal human antibody, so that they can be used in humans without eliciting an adverse immune response. Due to their similarities to normal human antibodies, they can be difficult to detect and quantify in human serum without the use of complementary antigens. At present, rapid, simple, highly sensitive, inexpensive assays to detect most of these therapeutic antibodies in human serum samples are not readily available. We have successfully developed a very simple, but extremely powerful scFv-based piezoimmunosensor assay platform to detect unique antibodies in serum samples. We propose in Aim 1 of this project to utilize a large (~2.9 billion member) phage-displayed antibody library to select for stable scFv recombinant antibodies specific for unique therapeutic antibodies. The therapeutic antibody-specific scFv will be used in lieu of traditional antigens for Aim 2 to develop piezoimmunosensors to detect and quantify therapeutic antibodies in human serum samples. The piezoimmunosensors will combine the high specificity and stability of scFv recognition of antigen (i.e. therapeutic antibody) with the low cost, one-step readout of non-label Quartz Crystal Microbalance transducers. Dr. Zeng, an analytical chemist, and Dr. Mernaugh, an immunologist, will carry out the proposed studies. Through their synergistic efforts, this team will create and certify a fast, accurate, highly sensitive and specific, stable, low cost diagnostic assay platform that can be used to detect and quantify therapeutic antibodies (e.g. Bevacizumab, Cetuximab, Panitumumab and Trastuzumab) in human serum samples. PUBLIC HEALTH RELEVANCE: The proposed research will focus on developing scFv recombinant antibodies and scFv-based piezoimmunosensor assays for use in detecting therapeutic antibodies in human serum samples. At present, rapid, simple, highly sensitive, inexpensive assays to detect most of therapeutic antibodies in human serum samples are not readily available. Since the proposed assay will be more sensitive than traditional immunoassay (e.g. ELISAs or whole antibody immunosensors) and can rapidly and accurately detect therapeutic antibodies in humans using a few drops of human serum and inexpensive instrumentation, a physician will be able to quickly determine if the concentration of therapeutic antibody in patients is sufficient or if therapy must be changed to benefit the patient.